RSVP local protection signaling reduction

ABSTRACT

In one example, a merge point network device (MP) receives a plurality of resource reservation request messages for establishing a plurality of label switched paths (LSPs), wherein each of the plurality of LSPs has a common point of local repair network device (PLR) and has the MP as a common MP, wherein each of the resource reservation request messages identifies a common bypass tunnel that extends between the PLR and the MP and avoids a protected resource. The MP stores an association between the bypass tunnel and each of the plurality of LSPs. The MP receives a single message to trigger creation at the merge point network device of backup LSP state information for all of the plurality of LSPs. In response to receiving the single message, the MP installs state information for all of the LSPs that correspond to the bypass tunnel according to the stored association.

This application is a continuation of U.S. patent application Ser. No.14/152,164 filed Jan. 10, 2014, the entire contents of which isincorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to packet-based computer networks and, moreparticularly, to forwarding packets within computer networks.

BACKGROUND

Routing devices within a network, often referred to as routers, maintainrouting information that describe available routes through the network.Upon receiving an incoming packet, the routers examine informationwithin the packet and forward the packet in accordance with the routinginformation. In order to maintain an accurate representation of thenetwork, routers exchange routing information in accordance with one ormore defined routing protocols, such as the Border Gateway Protocol(BGP).

Multi-protocol Label Switching (MPLS) is a mechanism used to engineertraffic patterns within Internet Protocol (IP) networks. By using MPLS,a source device can request a path through a network, i.e., a LabelSwitched Path (LSP). An LSP defines a distinct path through the networkto carry MPLS packets from the source device to a destination device. Ashort label associated with a particular LSP is affixed to packets thattravel through the network via the LSP. Routers along the pathcooperatively perform MPLS operations to forward the MPLS packets alongthe established path. LSPs may be used for a variety of trafficengineering purposes including bandwidth management and quality ofservice (QoS). A packet may be a formatted set of data.

A variety of protocols exist for establishing LSPs. For example, onesuch protocol is the label distribution protocol (LDP). Another type ofprotocol is a resource reservation protocol, such as the ResourceReservation Protocol with Traffic Engineering extensions (RSVP-TE).RSVP-TE uses constraint information, such as bandwidth availability, tocompute paths and establish LSPs along the paths within a network.RSVP-TE may use bandwidth availability information accumulated by alink-state interior routing protocol, such as the IntermediateSystem-Intermediate System (ISIS) protocol or the Open Shortest PathFirst (OSPF) protocol.

Head-end routers of an LSP are commonly known as ingress routers, whilerouters at the tail-end of the LSP are commonly known as egress routers.Ingress and egress routers, as well as intermediate routers along theLSP that support MPLS, are referred to generally as label switchingrouters (LSRs). A set of packets to be forwarded along the LSP isreferred to as a forwarding equivalence class (FEC). A plurality of FECsmay exist for each LSP, although there may, in some examples, be onlyone active LSP for any given FEC. Typically, a FEC definition includesthe IP address of the destination of the LSP, e.g., an IP addressassigned to the egress router of the LSP. In general, each router alongthe LSP maintains a context that associates a FEC with an incoming labeland an outgoing label. The ingress label edge router (LER) uses routinginformation, propagated from the egress LER, to determine the LSP, toassign labels for the LSP, and to affix a label to each packet of theFEC. The LSRs use MPLS protocols to receive MPLS label mappings fromdownstream LSRs and to advertise MPLS label mappings to upstream LSRs.When an LSR receives an MPLS packet from an upstream router, the LSRperforms a lookup in the context and swaps the MPLS label according tothe information in its forwarding table based on the lookup and forwardsthe packet to the appropriate downstream LSR or LER. The egress LERremoves the label from the packet and forwards the packet to itsdestination in accordance with non-label based packet forwardingtechniques.

SUMMARY

In general, this disclosure describes techniques for simplifying setupof backup LSPs along a common bypass tunnel between a point of localrepair (PLR) router and a merge point (MP) router, where the bypasstunnel is used for fast reroute of each of a plurality of protectedLSPs. This disclosure describes enabling use of a bypass tunnel orprotection path to minimize signaling at time of failure by firstsending information for protection state for each protected LSP at theMP router, and confirming by the PLR router that the message informationhas been received and understood by the MP router. In response todetecting a failure of a protected resource, the PLR router then sends asingle message to cause the MP router to create the state for eachprotected LSP using the previously sent information. In accordance withthe techniques of this disclosure, the PLR router assigns a bypasstunnel identifier to each bypass tunnel that the PLR router creates,which the PLR router sends to the MP router to facilitate this process.

In some examples, when sending Path messages for setting up LSPs thatare protected by a bypass tunnel, the PLR router includes within eachPath message a new signaling object that specifies the bypass tunnelidentifier of the bypass tunnel over which the LSP traffic will bererouted in case of failure. Upon receiving the Path message having thenew signaling object, the MP router stores a mapping between the LSPbeing established and the bypass tunnel identifier. This allows the PLRrouter to later, when a failure occurs, send only one Path message fortriggering creation of backup LSP state over the bypass tunnel. Thesingle Path message also includes the assigned bypass tunnel identifier.In response to receiving this single Path message over the bypasstunnel, the MP determines the bypass tunnel identifier specified by thePath message, and automatically creates state for each of the backupLSPs. By sending a single RSVP Path message on the bypass tunnel thatrefers to the earlier-advertised bypass tunnel identifier, the networkcan avoid sending a surge of RSVP Path and Resv messages immediatelyafter link failure. This can also facilitate streamlined setup ofsummary refresh of the backup LSP state over the bypass tunnel.

In one example, a method includes outputting, by a point of local repairnetwork device, a plurality of resource reservation request messages forestablishing a plurality of label switched paths (LSPs) between thepoint of local repair network device and a common merge point networkdevice, wherein each of the resource reservation request messagesidentifies a common bypass tunnel that extends between the point oflocal repair network device and the merge point network device andavoids a protected resource, and, by the point of local repair networkdevice, detecting failure of the protected resource along the pluralityof LSPs between the point of local repair network device and the mergepoint network device. The method also includes, in response to detectingthe failure, and by the point of local repair network device, outputtinga single message to the merge point network device to trigger creationat the merge point network device of backup LSP state information forall of the plurality of LSPs.

In another example, a method includes receiving, by a merge pointnetwork device, a plurality of resource reservation request messages forestablishing a plurality of LSPs between a common point of local repairnetwork device and the merge point network device, wherein each of theresource reservation request messages identifies a common bypass tunnelthat extends between the point of local repair network device and themerge point network device and avoids a protected resource, and, inresponse to receiving the plurality of resource reservation requestmessages, storing, by the merge point network device, an associationbetween the bypass tunnel and each of the plurality of LSPs. The methodalso includes receiving, by the merge point network device, a singlemessage to trigger creation of backup LSP state information for theprotected LSPs, and, in response to receiving the single message,automatically creating, by the merge point network device, backup LSPstate information for each of the plurality of LSPs that corresponds tothe bypass tunnel according to the stored association.

In another example aspect, a point of local repair network deviceincludes a hardware-based processor, and a Resource Reservation Protocolwith Traffic Engineering extensions (RSVP-TE) module executing on thehardware-based processor, wherein the RSVP-TE module outputs a pluralityof resource reservation request messages for establishing a plurality oflabel switched paths (LSPs) between the point of local repair networkdevice and a common merge point network device, wherein each of theresource reservation request messages identifies a common bypass tunnelthat extends between the point of local repair network device and themerge point network device and avoids a protected resource. The point oflocal repair network device also includes a connectivity fault detectionmodule that detects failure of the protected resource along theplurality of LSPs between the point of local repair network device andthe merge point network device, wherein in response to detecting thefailure, the RSVP-TE module outputs a single message to the merge pointnetwork device to trigger creation of backup LSP state information atthe merge point network device for all of the plurality of LSPs.

In yet another example aspect, a merge point network device includes ahardware-based processor, and a RSVP-TE module executing on thehardware-based processor, wherein the RSVP-TE module receives aplurality of resource reservation request messages for establishing aplurality of LSPs between a common point of local repair network deviceand the merge point network device, wherein each of the resourcereservation request messages identifies a common bypass tunnel thatextends between the point of local repair network device and the mergepoint network device and avoids a protected resource, wherein theRSVP-TE module stores an association between the bypass tunnel and eachof the plurality of LSPs, and outputs a single message to the mergepoint network device to trigger creation at the merge point networkdevice of backup LSP state information for all of the plurality of LSPs,and wherein, in response to receiving the single message, the RSVP-TEmodule creates backup LSP state information for each of the plurality ofLSPs that corresponds to the bypass tunnel according to the storedassociation.

In a further example aspect, a computer-readable storage medium includesinstructions for causing a programmable processor to output a pluralityof first resource reservation request messages for establishing aplurality of label switched paths (LSPs) between the point of localrepair network device and a common merge point network device, whereineach of the resource reservation request messages identifies a commonbypass tunnel that extends between the point of local repair networkdevice and the merge point network device and avoids a protectedresource, detect failure of the protected resource along the pluralityof LSPs between the point of local repair network device and the mergepoint network device, and, in response to detecting the failure, outputa single message to the merge point network device to trigger creationat the merge point network device of backup LSP state information forall of the plurality of LSPs.

The techniques of this disclosure may provide one or more advantages.For example, The techniques of this disclosure provide a solution thatreduces or avoids the need to send RSVP trigger messages for all of thebackup LSPs through a bypass tunnel, and thus makes it possible to scaleto a higher number of protected LSPs using a given bypass tunnel. Bysending a single RSVP Path message on the bypass tunnel that refers tothe earlier-advertised bypass tunnel identifier, the network can avoidsending a surge of RSVP Path and Resv messages immediately after linkfailure.

The techniques of this disclosure also mean that the PLR router does notneed to signal the Backup LSPs ahead of time, which may avoid redundantwork and an unnecessary increase in the number of LSPs to be maintained.The techniques of this disclosure can also enable customers to make useof default RSVP refresh timers, thus avoiding a need to increase theRSVP default refresh time. Increasing the RSVP default refresh time canresult in longer delays in re-synchronizing state if some RSVP updatemessages are lost, and may not be an acceptable solution to allcustomers.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example system in whichrouters are configured to forward network traffic in accordance with thetechniques of this disclosure.

FIG. 2 is a block diagram illustrating an example embodiment of a pointof local repair (PLR) network device in accordance with the techniquesof this disclosure.

FIG. 3 is a block diagram illustrating an example embodiment of a mergepoint (MP) network device in accordance with the techniques of thisdisclosure.

FIGS. 4 and 5 are flowcharts illustrating example operation of networkdevices in accordance with the techniques of this disclosure.

DETAILED DESCRIPTION

FIG. 1 is a block diagram illustrating an example network system 10 inwhich provider edge (PE) routers 12A-12D (“PE routers 12”) and routers16A-16C (“routers 16”) of network 14 are configured to forward networktraffic (e.g., network packets) in accordance with the techniques ofthis disclosure. In the example of FIG. 1, router 16A is a point oflocal repair (PLR) router along the path of each of label switched paths(LSPs) 22A-22D (“LSPs 22”). In the example of FIG. 1, PLR router 16A isa transit router, i.e., an intermediate router along LSPs 22 and isneither an ingress router nor an egress router of the LSPs. In thisexample, PE router 12A is the ingress router of LSPs 22A, 22B, and 22C,and PE router 12B is the egress router of LSPs 22A, 22B, and 22C. PErouter 12C is the ingress router of LSP 22D, and PE router 12D is theegress router of LSP 22D. Each of LSPs 22 extends along respective pathsthat pass through PLR router 16A, link 20, and router 16B.

PE routers 12 and routers 16 represent any network device that routes orotherwise forwards traffic through network 14. Typically, routers 12, 16represent a L3 packet-switching device that operates at L3 to exchangerouting information using a routing protocol, such as an InteriorGateway Protocol (IGP), describing a current topology of network 14.Routers 12, 16 then process this routing information, selecting pathsthrough its representation of the topology of network 14 to reach allavailable destinations to generate forwarding information. In otherwords, routers 12, 16 reduce these paths to so-called “next hops” whichidentify interfaces to which to forward traffic destined for aparticular destination, where the forwarding information includes thislist of next hops. Routers 12, 16 then install this forwardinginformation in a forwarding plane of the router, whereupon theforwarding plane forwards received traffic in accordance with theforwarding information.

PLR router 16A may have previously computed and signaled bypass tunnel26 as a backup path for protecting link 20, such as by using theResource Reservation Protocol with Traffic Engineering extensions(RSVP-TE). PLR router 16A is the point of local repair (PLR) for bypasstunnel 26, and router 16B is the merge point (MP) for bypass tunnel 26.Bypass tunnel 26 is a tunnel that provides link protection for link 20between router 16A and router 16B, such that if link 20 should fail, PLRrouter 16A can establish a backup LSP over bypass tunnel 26 and send thenetwork traffic received along an existing LSP through the backup LSP.Router 16A may establish bypass tunnel 26 in accordance with MPLS fastreroute techniques, as described in P. Pan, “Fast Reroute Extensions toRSVP-TE for LSP Tunnels,” Network Working Group RFC 4090, May 2005, theentire contents of which are incorporated by reference herein.

For example, as the point of local repair (PLR) and ingress of bypasstunnel 26, router 16A may establish bypass tunnel 26 to protect one ormore other existing LSPs (such as LSPs 22) that traverse at least router16A and router 16B and do not traverse router 16C. In some examples,router 16A may establish bypass tunnel 26 upon request by an ingressrouter of one of these protected LSPs 22. For example, router 16A mayreceive an RSVP-TE PATH request from ingress PE router 12A that includesa fast reroute object in which a “local protection desired” flag, orother fast reroute flag, is set. After router 16A establishes bypasstunnel 26, router 16A maintains forwarding information in a data planeof router 16A that allows router 16A to send traffic through bypasstunnel 26 if link 20 fails.

Responsive to detecting a failed resource between PLR router 16A and MProuter 16B (e.g., failure of link 20, in the example of FIG. 1), PLRrouter 16A may perform a soft reroute action to reroute the traffic LSPs22 onto a previously-established bypass tunnel 26. For example, PLRrouter 16A may update its stored forwarding state to change the primarynext hops for LSPs 22, such as by setting a next hop for bypass tunnel26 as the primary next hop for traffic received for LSPs 22.

In some examples, network 14 may be a service provider network. Forexample, network 14 may represent one or more networks owned andoperated by a service provider (which is commonly a private entity) thatoffer one or more services for consumption by subscriber networks. Inthis context, network 14 is typically a layer three (L3) packet-switchednetwork that provides L3 connectivity between a public network and oneor more subscriber networks (not shown). Often, this L3 connectivityprovided by a service provider network is marketed as a data service orInternet service, and subscribers may subscribe to this data service.Network 14 may represent a L3 packet-switched network that providesdata, voice, television and any other type of service for purchase bysubscribers and subsequent consumption by subscriber networks.

While not shown in the example of FIG. 1, network system 10 may includeadditional service provider networks, subscriber networks and othertypes of networks, such as access networks, private networks, or anyother type of network commonly employed to deliver one or more services(such as data service, Internet Protocol Television (IPTV) service,voice over Internet Protocol (VoIP) service, video telephony service orany other type of service) to subscriber networks.

RFC 4090 describes a facility backup method which provides link or nodeprotection by pre-calculating a bypass path for the set of LSPstraversing a link. See P. Pan, “Fast Reroute Extensions to RSVP-TE forLSPs,” Network Working Group RFC 4090, May 2005, the entire contents ofwhich are incorporated by reference herein. Upon link failure, PLRrouter 16A redirects traffic over bypass tunnel 26 via a backup LSP fromPLR router 16A to MP router 16B. Because of the soft-state nature ofRSVP, PLR router 16A is also expected to signal the backup LSPs alongthe bypass tunnel 26 towards MP router 16B. These backup LSPs help inmaintaining state across PLR router 16A and MP router 16B.

Although shown in FIG. 1 for purposes of example as having four LSPs 22,there may be many more than four LSPs in network 14 established throughPLR router 16A and MP router 16B. Consider a setup where a large numberof protected LSPs 22 are using the same primary link 20. All these LSPswill then use the same bypass tunnel 26. When local protection is in useand a failure of a protected resource occurs (e.g., link 20 goes down),conventionally PLR router 16A would need to signal a new backup LSPsacross bypass tunnel 26 for each of the protected LSPs 22 via RSVPBackup Path messages. This signaling of backup LSPs is required at acritical time when there is already a lot of churn in network 14. Inthis scenario, PLR router 16A would waste a lot of important cycles insignaling these backup Path messages. PLR router 16A will also bereceiving a large number of RESV messages on the backup tunnel 26 fromMP router 16B. Some of the backup PATH messages may get lost or PLRrouter 16A might not be able to signal all the backup PATH messagesbefore state timeouts at MP router 16B. For example, after a linkfailure, if MP router 16B does not receive a Backup Path message within3*REFRESH TIME, then Path state is timed out at MP router 16B. Itresults in MP router 16B sending a PathTear downstream. If backup Pathmessage signaled by PLR router 16A reaches after this Path timeout at MProuter 16B, then MP router 16B may interpret the Path message as beingfor a new LSP because MP router 16B cannot correlate the Path message toany existing protected LSP 22, and MP router 16B will signal the Pathmessage towards the egress device.

The techniques of this disclosure provide a solution that reduces oravoids the need to send RSVP trigger messages for all of the backup LSPsthrough bypass tunnel 26, and thus makes it possible to scale to ahigher number of protected LSPs using bypass tunnel 26. In accordancewith the techniques of this disclosure, PLR router 16A will assign anidentifier to each bypass tunnel that PLR router 16A creates. PLR router16A will include a new signaling object “BypassInfo” in the Path messageof every protected LSP. The BypassInfo signaling object identifies thebypass tunnel used for protecting the LSP and makes that informationknown to the merge point (MP). For example, PLR router 16A sends aplurality of resource reservation request messages (e.g., RSVP-TE Pathmessages) 18A-18D (“Path messages 18”) corresponding to respective LSPs22A-22D, for establishing the LSPs 22.

The MP is usually one or two hops downstream of the PLR router 16A, andso the signaling object containing the bypass tunnel identifier includesa mechanism to discard the information from the Path message once itgoes beyond the MP (e.g. a TTL value or explicit identification of theintended MP). The intended MP will remove this new signaling object fromPATH message, because this signaling object is of no interest to nodesfurther downstream. The signaling object identifies the PLR that createdthe signaling object and the intended MP for the signaling object. Thatensures that the (PLR, MP, bypass tunnel identifier) tuple is a uniqueidentifier in the network. To this end, the “BypassInfo” object maycontain, for example, a bypass tunnel identifier, which is a value foridentifying the bypass tunnel associated with the protected LSP; a PLRID, which is a Router ID of the PLR so that the MP can identify the PLRcorrectly; and MP ID, which is a Router ID of the MP so that the newsignaling object is processed at the correct MP.

MP router 16B should send an acknowledgement message (ACK) to the PLRrouter 16A to indicate that MP router 16B has received and processed theBypassInfo object. So, upon receipt of this new signaling object in thePath message, MP router 16B will include a new signaling object“BypassInfoACK” in a resource reservation reply message (e.g., anRSVP-TE Resv message). For example, MP router 16B sends Resv messages19A-19D (“Resv messages 19”), in response to the respective Path message18A-18D received from PLR router 16A. The “BypassInfoACK” signalingobject will contain the (PLR, MP, Bypass Tunnel Identifier) tuple, i.e.,Bypass Tunnel Identifier value, PLR ID-Router ID of PLR, and MPID-Router ID of MP. PLR router 16A determines that MP router 16B hasreceived and processed the bypass info signaling object when PLR router16A receives a corresponding signaling object back in the Resv message19.

When link failure happens, PLR router 16A will send a new object“BypassInUse” in a message to MP router 16B. Now when a failure occursand the bypass tunnel comes into use, PLR router 16A will notify MProuter 16B by sending a BypassInUse signaling object which includes thebypass tunnel identifier value. In accordance with the techniques ofthis disclosure, PLR router 16A may send a single bypass Path message 24to MP router 16B with the BypassInUse signaling object, instead ofsending multiple (one for each protected LSP) trigger backup Pathmessages through the bypass tunnel 26. MP router 16B can now use thebypass tunnel identifier as the trigger for causing MP router 16B tocreate the backup LSP state for all of the protected LSPs. In responseto receiving the single bypass Path message 24, for each protected LSPwith a matching bypass tunnel identifier, MP router 16B will create thebackup state as if MP router 16B had received a Path message for thebackup LSP through the bypass tunnel.

PLR router 16A can send the BypassInUse signaling object to MP router16B in various ways. In some examples, PLR router 16A may add theBypassInUse signaling object to the signaling of bypass tunnel 26, e.g.,by including the BypassInUse signaling object within a Path message thatPLR router 16A sends to MP router 16B for maintaining/refreshing bypasstunnel 26. In this example, the existing bypass Path message sent fromPLR router 16A to router 16C to MP router 16B (which needs to beperiodically sent to maintain bypass tunnel 26) is used by PLR router16A as a transport vehicle for sending the BypassInUse signaling object.In other examples, PLR router 16A includes the BypassInUse signalingobject as part of some message sent “over” bypass tunnel 26, i.e., theBypassInUse signaling object is transparent to router 16C. In this case,for example, the message may be prepended with the MPLS label assignedfor bypass tunnel 26, and this could be a new RSVP signaling messagetype. In either example, PLR router 16A sends a single message to MProuter 16B to trigger MP router 16B to establish all of the neededbackup LSP state on MP router 16B.

At the time of failure, for the LSPs which are missing acknowledgmentfrom MP router 16B of the bypass information signaling object, PLRrouter 16A will continue to send backup Path messages to trigger MProuter 16B as normal. This will ensure correct behavior in cases whereMP router 16B is not supporting this new functionality, or if MP router16B has not correctly processed the new signaling object.

On receiving the single Path message with the BypassInUse signalingobject, MP router 16B will start the creation of backup LSP state. MProuter 16B will create the backup state for each protected LSP withmatching bypass tunnel identifier. MP router 16B will also send to PLRrouter 16A a single Resv message 25 having a BypassInUse Acknowledgementsignaling object 25, in response to the received single Path message, aspart of bypass tunnel signaling. At the time of link failure, if PLRrouter 16A has not received “BypassInfoAck” object for some LSPs, thenPLR router 16A will continue to trigger Backup Path messages for thoseLSPs.

The techniques of this disclosure also provide a mechanism to extend therefresh reduction capabilities for backup LSPs. Because of thesoft-state nature of RSVP, PLR router 16A and MP router 16B willeventually need to resume the standard RSVP refresh behavior andexchange Path and Resv messages for the backup LSPs. To reduce theoverhead of that, the techniques of this disclosure further include amechanism to bootstrap refresh reduction functionality between PLRrouter 16A and MP router 16B. Refresh reduction functionality isdescribed in L. Berger, “RSVP Refresh Overhead Reduction Extensions,”Network Working Group RFC 2961, April 2001, the entire contents of whichare incorporated by reference herein. The refresh reductionfunctionality aspect of this disclosure has the goal to make backupmessage IDs available for the Path and Resv state so that PLR router 16Anever has to send the actual individual trigger Path and Resv messagesover bypass tunnel 26. For the Path state, this goal is achieved byincluding a backup message-ID along with the bypass tunnel identifier inthe same signaling object in the initial protected LSP Path message 18sent by PLR router 16A over the primary path. Doing so enables MP router16B to learn about the message-ID to put in the backup LSP state that MProuter 16B later automatically creates for PLR router 16A.

MP router 16B can likewise include a respective BackupResv Message-ID inthe respective BypassInfoAck Objects of the Resv messages 19 sent by MProuter 16B over the primary path when establishing LSPs 22. Forestablishing Resv state message-IDs, MP router 16B includes Resvmessage-IDs for the protected LSPs in the new signaling object containedin the Resv messages 19. Pre-sending these message-IDs allow the MProuter 16B and PLR router 16A to store the message-IDs, allowing them toidentify the message-IDs that are received in later-sent summary refreshmessages, and be able to appropriately process the summary refreshmessages.

There can be more than one such bypass tunnel identifier because MProuter 16B may be a MP for more than one upstream PLR. This Resv bypassinfo ack signaling object explicitly identifies the PLR that the messageis targeting and will not be propagated in Resv messages beyond(upstream from) the PLR. The Resv bypass info ack signaling objectincludes the message-ID to be used for the backup Resv message (from MPto PLR) corresponding to the protected LSP.

This a-priori establishment of message-IDs enables the followingmechanism to synchronize and maintain the backup LSP state between PLRand MP: after the initial single Path message subsequently sent acrossthe bypass tunnel 26 from PLR router 16A to MP router 16B whichestablishes the backup LSPs, both PLR router 16A and MP router 16B sendSummary refresh messages to each other containing a list of thepre-assigned message-IDs. Any differences between PLR router 16A and MProuter 16B views of what backup LSPs should exist can be resolved by theMESSAGE_ID_ACK and MESSAGE_ID_NACK mechanism described in RFC 2961.

In response to determining that the failed resource (e.g., link 20) hascome back up, PLR router 16A will no longer include the new bypassinformation signaling object in the bypass Path message, and PLR router16A will stop sending summary refresh messages corresponding to thebackup LSPs. MP router 16B will then in turn also stop sending summaryrefresh messages corresponding to the backup LSPs.

FIG. 2 is a block diagram illustrating an example embodiment of a pointof local repair (PLR) network device in accordance with the techniquesof this disclosure. PLR router 30 may, for example, represent any ofrouters 12 or 16 of FIG. 1, such as PLR router 16A, for example. In thisexample, PLR router 30 includes a control unit 31 that comprises arouting component 32 and a forwarding component 34. In addition, PLRrouter 30 includes a set of interface cards (IFCs) 50A-50N(collectively, “IFCs 50”) for communicating packets via inbound links52A-52N (collectively, “inbound links 52”) and outbound links 54A-54N(collectively, “outbound links 54”).

Routing component 32 primarily provides an operating environment forcontrol plane protocols 40. For example, one or more IGP routingprotocols 42, such as Intermediate System to Intermediate System (ISIS)routing protocol 42A, or the Open Shortest Path First (OSPF) routingprotocol 42B, maintain routing information 36 to reflect the currenttopology of a network and other network entities to which PLR router 30is connected. In particular, IGPs 42 update routing information 36 toaccurately reflect the topology of the network and other entities. PLRrouter 30 may include other example routing protocols such as BorderGateway Protocol (BGP).

Routing component 32 generates and programs forwarding component 34 withFIB 38 that associates network destinations with specific next hops andcorresponding interfaces ports of IFCs 50 in accordance with routinginformation 36. Routing component 32 may generate FIB 38 in the form ofa radix tree having leaf nodes that represent destinations within thenetwork, for example.

Based on FIB 38, forwarding component 34 forwards packets received frominbound links 52A-52N to outbound links 54A-54N that correspond to nexthops associated with destinations of the packets. U.S. Pat. No.7,184,437 provides details on an exemplary embodiment of a router thatutilizes a radix tree for route resolution. The entire contents of U.S.Pat. No. 7,184,437 are incorporated herein by reference.

In one example, forwarding component 34 is a rich and dynamic sharedforwarding plane, optionally distributed over a multi-chassis router.Moreover, forwarding component 34 may be provided by dedicatedforwarding integrated circuits normally associated with high-end routingcomponents of a network router. Further details of one exampleembodiment of PLR router 30 can be found in U.S. Pat. No. 8,339,959,issued Dec. 25, 2012, entitled “STREAMLINED PACKET FORWARDING USINGDYNAMIC FILTERS FOR ROUTING AND SECURITY IN A SHARED FORWARDING PLANE,”the entire contents of which are incorporated herein by reference.

As shown in FIG. 2, protocols 40 executing within routing component 32includes one or more MPLS protocols for establishing a LSP, which may beaccumulated by IGPs 42. For example, RSVP-TE 45 may generate andmaintain a traffic engineering database 49, including bandwidthreservations for paths associated with MPLS LSPs. Constrained ShortestPath First (CSPF) process 48 computes a shortest path or paths for anMPLS LSP based on specified constraints and bandwidth availabilityinformation associated with the links within the network. IGPs 42 may,in turn, advertise the calculated bandwidth availability information intraffic engineering database (TED) 49 to other peer routers. As anotherexample, constrained Label Distribution Protocol (CR-LDP) 44 may sendand receive label mapping messages for establishing a LSP.

PLR router 30 receives RSVP-TE Path messages from PE routers 12A and 12Cfor setting up LSPs 22A and 22B, respectively. In response, RSVP-TEmodule 45 of router 30 forwards the RSVP-TE Path messages to router 16B,and also sends RSVP-TE Resv messages back to the ingress routersconfirming the reservation of the requested bandwidth. RSVP-TE module 45may also inform IGPs 42, which in turn can update TED 49 with currentavailable bandwidth information. IGPs 42 may also forward the updatedcurrent available bandwidth information to other IGP peers. RSVP-TEmodule 45 may also store MPLS labels to FIB 38 for LSPs 22A and 22B.

Subsequent to LSPs 22 being established, PLR router 30 may in someexamples detect a failure condition of a link, such as link 20 (FIG. 1).For example, connectivity fault detection module 62 may run a session onlink 20, and can detect when link 20 fails. In some examples, the link20 is managed by the kernel of router 30, and the routing protocoldaemon (RPD) and/or RSVP-TE module 45 is informed by the kernel if thereis any change. RSVP-TE module 45 will react depending on itsconfiguration. In the example of a one-hop session (IGP) at a transitrouter adjacent to the failed link, then a Periodic Packet ManagementDaemon (PPMD) (not shown) of routing component 32 may delegateconnectivity fault detection functionality to a forwarding componentmonitor module (e.g., pfemon). Otherwise, routing component 32 may dofault detection. Example techniques for connectivity fault detection ina multi-chassis routing system are described in U.S. Pat. No. 7,720,061,filed Aug. 18, 2006, entitled “Distributed Solution for ManagingPeriodic Communications in a Multi-Chassis Routing System,” the entirecontents of which are incorporated by reference herein. In someexamples, in response to detecting a failure condition of a protectedresource between PLR router 30 and a merge point router, connectivityfault detection module 62 informs RSVP module 45 in the control plane ofrouter 30 of the detected condition. In other examples, connectivityfault detection module 62 may detect a node failure condition, such aswhere an intermediate router is present on the path between the PLRrouter 30 and a merge point router.

Although illustrated for purposes of example as being positioned in theforwarding component 34 (e.g., in the forwarding plane of PLR router30), connectivity fault detection module 62 could alternatively belocated in the control plane of PLR router 30, such as within routingcomponent 32. In the case of connectivity fault detection module 62being located in the control plane, connectivity fault detection module62 may poll the forwarding component 34 for statistics and information,and compare the data received from forwarding component 34 to configuredthresholds, for example. In one example, connectivity fault detectionmodule 62 may comprise a software application programming interface(API) in the control plane of PLR router 30 that notifies notify thecontrol plane of the status of aspects of forwarding component 34, suchas next hop utilization statistics, and forwarding component 34 respondsby providing the requested statistics. In this case, connectivity faultdetection module 62 might perform bookkeeping/accounting of bandwidth inthe control plane, for example.

In accordance with the techniques of this disclosure, RSVP-TE module 45operates in accordance with an RSVP-TE protocol that has been extendedto include features for simplifying setup of backup LSPs along a commonbypass tunnel between PLR router 30 and a merge point (MP) router, wherethe bypass tunnel is used for fast reroute of each of a plurality ofprotected LSPs. RSVP-TE module 45 includes bypass info module 56, whichassigns a bypass tunnel identifier to each bypass tunnel created byRSVP-TE module 45. Bypass info module 56 selects the bypass tunnelidentifiers in a manner such that a change in bypass LSPs does notrequiring sending a new identifier in trigger Path messages for allaffected primary LSPs. When there is a need to re-route the bypasstunnel due to changes in the network, the new bypass tunnel taking thenew path should still have the same identifier as before. The idea is tohave a somewhat persistent identifier for a bypass tunnel protecting aparticular link (or node). This may avoid churn when signaling theprotected LSPs. In this manner, the identifier for a bypass tunnelprotecting a particular resource (link or node) remains the same even asthe bypass tunnel's instantiation changes over time to adapt to networkconditions. Bypass info module 56 can use an algorithm for selecting theidentifier of the bypass tunnel used by primary LSPs such that as thebypass tunnel is changed and rerouted, the identifier does not change,and thus the primary LSPs do not need to be re-signaled with a differentidentifier. For example, the identifier can be tied to the particularresource (link or node) whose failure is being protected against.

RSVP-TE module 45 stores the mapping of bypass tunnel identifiers tobypass tunnels (and protected LSPs) to bypass tunnel identifiers 58.There may be multiple bypass tunnel identifiers assigned to multipledifferent bypass tunnels for which PLR router 30 is a PLR. When sendingthe Path messages for setting up LSPs that are protected by the bypasstunnel, bypass info module 56 includes within each Path message a bypassinformation signaling object that specifies the assigned bypass tunnelidentifier of the bypass tunnel over which the LSP traffic will bererouted in case of failure. The bypass information signaling objectalso may specify a PLR ID of PLR router 30, and an MP ID of the MP thatis the egress of the bypass tunnel. In some examples, the bypassinformation signaling object also includes a message-ID assigned to theLSP for backup Path state. As described below with respect to FIG. 3,the MP router that receives the Path messages having the bypassinformation signaling object will store state associating the LSPs forwhich the Path messages are being sent with the bypass tunnelidentifier, and may store the message-IDs for later use.

RSVP-TE module 45 of PLR router 30 receives a Resv message from the MProuter with a bypass information acknowledgement signaling object. Insome examples, RSVP-TE module 45 may similarly check the PLR ID of thereceived bypass information acknowledgement signaling object todetermine whether the PLR ID corresponds to PLR module 30. In someexamples, the bypass information acknowledgement signaling object alsoincludes a message-ID assigned to the LSP for backup Resv state. RSVP-TEmodule 45 stores the label mapping information from the received Resvmessage in FIB 38, and stores bypass-info-ack state 60 indicating whichLSPs have received the bypass information acknowledgement signalingobject, and may store the message-IDs for later use.

Subsequently, when connectivity fault detection module 62 determinesthat a protected resource has failed, connectivity fault detectionmodule 62 can notify RSVP-TE module 45. After detecting failure of aprotected resource, RSVP-TE module 45 of PLR router 30 may also updateFIB 38 to set a next hop to router 16C along bypass tunnel 26 as theprimary next hop, such as by changing weights associated with the nexthops in the forwarding information. In some examples, PLR router 30 mayalso then delete the next hop along link 20 from the forwarding state.Examples of updating forwarding state for fast reroute are described inU.S. Pat. No. 8,077,726, entitled, “FAST REROUTE FOR MULTIPLE LABELSWITCHED PATHS SHARING A SINGLE INTERFACE,” issued Dec. 13, 2011, theentire contents of which are incorporated by reference herein.

Also in response to connectivity fault detection module 62 notifyingRSVP-TE module 45 of the failure, bypass info module 56 can send asingle message for triggering creation of backup LSP state for each ofthe LSPs 22 over the bypass tunnel (e.g., a Path message for signalingthe bypass tunnel). The single message also includes the assigned bypasstunnel identifier. In response to receiving a single message included aspart of the bypass tunnel signaling, for example, the MP determines thebypass tunnel identifier specified by the message, and automaticallycreates state for each of the backup LSPs. The state is created by theMP to simulate that state which the MP would have created in response toreceiving multiple individual Path messages signaling each respectivebypass LSP. By sending a single message, such as an RSVP Path message,that refers to the earlier-advertised bypass tunnel identifier, thenetwork can avoid sending a surge of RSVP Path and Resv messagesimmediately after link failure.

PLR router 30 receives the single Resv message from the MP router, andin response, bypass info module 56 of PLR router 30 creates backup LSPstate 64, which includes the backup Resv message-IDs previously receivedfor the protected LSPs being run over bypass tunnel 26. PLR router 30creates the state in a manner that simulates the state which PLR router30 would have created in response to receiving multiple individual Resvmessages signaling each respective bypass LSP. PLR router 30 also sendssummary refresh messages to the MP using the same Path message-IDs thatPLR router 30 had previously sent to the MP router in the initial Pathmessages for establishing LSPs 22. PLR router 30 continues to send thesummary refresh messages to the MP until RSVP-TE module 45 is informedthat the protected resource has once again become operational.

PLR router 30 also includes management interface 46 by which anadministrator (“ADMIN”), script, or network management system canconfigure PLR router 30. In some examples, management interface 46 maybe presented locally, or may be used for receiving information by way ofan Application Programming Interface (API) from a Software DefinedNetwork (SDN) controller or Path Computation Element (PCE), for example.

FIG. 3 is a block diagram illustrating an example embodiment of a mergepoint (MP) network device in accordance with the techniques of thisdisclosure. MP router 75 may, for example, represent any of routers 12or 16 of FIG. 1, such as MP router 16B, for example. MP router 75includes many of the same components as described in FIG. 2, and thesehave similar functionality as described there. In some examples, arouter may be both a PLR router and as a MP router for different bypasstunnels. In this case, the router may include components of both PLRrouter 30 (FIG. 2) in addition to those of MP router 75.

Upon receiving a Path message having the bypass information signalingobject, bypass info module 56 stores a mapping between the bypass tunnelidentifier and the LSP (e.g., as identified by the FEC specified by theRSVP-TE Path message). The Path message may also include a message-ID,which MP router 75 stores for later use in creating backup LSP state.

After a protected resource fails, MP router 75 receives a single Pathmessage from the PLR router for triggering MP router 75 to create backupLSP state 72 for each of the backup LSPs over the bypass tunnel. Thesingle Path message includes the assigned bypass tunnel identifier. Inresponse to receiving this single Path message included as part of thebypass tunnel signaling, bypass info module 56 determines the bypasstunnel identifier specified by the Path message, and refers to LSP tobypass tunnel mappings 70 to determine which LSPs are associated withthat bypass tunnel identifier. Bypass info module 56 automaticallycreates and installs backup LSP state 72 for the protected LSPs 22, andmay also associated the previously-received message-IDs with the backupLSPs for use in correctly processing received summary refresh messagesfor backup LSPs associated with the determined LSPs.

FIG. 4 is a flowchart illustrating example operation of network devicesin accordance with the techniques of this disclosure. FIG. 4 will bedescribed with reference to FIGS. 1-3 for purposes of example. Forexample, FIG. 4 refers to a PLR network device and a MP network device,which in one example may be PLR router 16A and MP router 16B of FIG. 1,respectively.

In the example of FIG. 4, for each of several LSPs, PLR router 16A sendsa respective resource reservation message (e.g., an RSVP-TE Pathmessage) for establishing the respective LSP, and each of the resourcereservation messages includes a bypass information signaling object, inaccordance with the techniques of this disclosure (100). The bypassinformation signaling object may include, for example, one or morefields specifying a bypass tunnel identifier value that identifies thebypass tunnel over which the respective LSP will be rerouted in case offailure, and may also specify an identifier of the PLR router and anidentifier of the MP router. PLR router 16A assigns a bypass tunnelidentifier value to each bypass tunnel for which PLR router 16A is theingress device, and stores the bypass tunnel identifiers and anindication of the LSPs to which they are mapped to bypass tunnelidentifiers 58. In some examples, the resource reservation messages alsoeach include a respective message-ID for backup Path state with thebypass information signaling object to be used by MP router 16B inprocessing subsequently received summary refresh messages for acorresponding backup LSP over bypass tunnel 26.

MP router 16B receives the several resource reservation messages fromPLR router 16A (102), and, for each received message, RSVP-TE module 45of MP router 16B reserves bandwidth and allocates an MPLS label inaccordance with RSVP-TE (103). Bypass info module 56 of RSVP-TE module45 also processes the bypass information signaling object containedwithin each of the resource reservation messages. Bypass info module 56is configured to understand the bypass information signaling objects andprocess them appropriately.

Bypass info module 56 inspects the bypass information signaling objectand determines whether the merge point identifier (“MP ID”) (e.g., an IPaddress) specified by the bypass information signaling objectcorresponds to MP router 16B (104). If the MP ID of the bypassinformation signaling object does not correspond to that of MP router16B (NO branch of 104), RSVP-TE module 45 forwards the path message tothe next network device along the path as specified by the explicitroute object (ERO) of the path message (110). If the MP ID of the bypassinformation signaling object does correspond to that of MP router 16B(YES branch of 104), bypass info module 56 stores information from thebypass information signaling object, such as by storing to LSP to bypasstunnel mappings 70 a mapping between the LSP (e.g., as identified by theforwarding equivalence class (FEC) specified in the Path message) andthe bypass tunnel identifier (106). Bypass info module 56 may also storeany message-IDs included with the resource reservation request messages,with an indication of the LSPs to which the message-IDs map, for backupPath state to be created by MP router 16B and used for processingsubsequently received summary refresh messages for a correspondingbackup LSP over bypass tunnel 26. Bypass info module 56 then removes thebypass information signaling object from the Path message (108), andforwards the path message to the next network device along the path ofthe LSP, if any, according to the ERO of the Path message (110).

RSVP-TE module 45 generates and sends to PLR router 16A a resourcereservation reply message (e.g., an RSVP-TE Resv message) that includesthe allocated label and confirms that the requested resources have beenreserved along the specified path. In accordance with the techniques ofthis disclosure, the Resv message also includes a bypass informationacknowledgement signaling object that specifies the (bypass tunnelidentifier, PLR, MP) tuple, the same as in the corresponding receivedbypass information signaling object for which receipt is beingacknowledged (112). In some examples, the bypass informationacknowledgement signaling object of each of the Resv messages alsoincludes a respective message-ID for backup Resv state for thecorresponding backup LSP that will later be established. RSVP-TE module45 of PLR router 16A receives the Resv message with the bypassinformation acknowledgement signaling object (114). In some examples,bypass info module 56 of RSVP-TE module 45 may similarly check the PLRID of the received bypass information acknowledgement signaling objectto determine whether the PLR ID corresponds to PLR module 16A. If so,RSVP-TE module 45 stores the label mapping information from the receivedResv message in forwarding information (e.g., FIB 38), and storesbypass-info-ack state 60 indicating which LSPs have received the bypassinformation acknowledgement signaling object (116).

Bypass info module 56 may also store any message-IDs that were includedwith the Resv messages, with an indication of the LSPs to which themessage-IDs map, for later backup Resv state to be created by PLR router16A for use in processing subsequently received summary refresh messagesfor a corresponding backup LSP over bypass tunnel 26. If the PLR ID ofthe received bypass information acknowledgement signaling object doesnot correspond to PLR module 16A, PLR module 16A forwards the pathmessage to the next network device along the path of the LSP accordingto the ERO of the Resv message.

FIG. 5 is a flowchart illustrating example operation of network devicesin accordance with the techniques of this disclosure. FIG. 5 will bedescribed with reference to FIGS. 1-3 for purposes of example. Forexample, FIG. 5 refers to a PLR network device and a MP network device,which in one example may be PLR router 16A and MP router 16B of FIG. 1,respectively.

PLR router 16A detects a failure of a protected resource, e.g., byconnectivity fault detection module 62 (120). The protected resource maybe, for example, a protected link (e.g., link 20 of FIG. 1), or aprotected node (e.g., a network device such as a router). In response todetecting the failure of the protected resource, RSVP-TE module 45 ofPLR router 16A generates and outputs a single message (e.g., an RSVP-TEPath message as part of signaling of bypass tunnel 26) for all of theLSPs 22 for which a bypass information acknowledgement signaling objecthaving the identifier of bypass tunnel 26 was previously received fromMP router 16B (122). The single message includes a “bypass in use”signaling object that specifies the bypass tunnel identifier, toindicate to MP router 16B that bypass tunnel 26 will now be used forforwarding traffic on the protected LSPs 22 to MP router 16B.

MP router 16B receives the single message from PLR router 16A (124), andin response, bypass info module 56 of MP router 16B creates backup LSPstate 72 for all of the protected LSPs associated with the bypass tunnelidentifier (e.g., by referring to LSP to bypass tunnel mappings 70),which will now run over bypass tunnel 26 after failure of the protectedresource (126). Bypass info module 56 also associates the previouslyreceived backup message-IDs with the respective backup LSP state. Inaccordance with the techniques of this disclosure, PLR router 16A cansend only a single message having the bypass in use signaling object,from which the RSVP-TE module 45 of MP router 16B is configured toautomatically create the backup LSP state 72 for each of the protectedLSPs 22 that bypass info module 56 determines is mapped to the bypasstunnel identifier carried in the bypass in use signaling object based onLSP to bypass tunnel mappings 70.

Bypass info module 56 of MP router 16B then sends a single message forall of the protected LSPs (128) (e.g., an RSVP-TE Resv message forsignaling bypass tunnel 26). The single message includes a “bypass inuse” acknowledgement signaling object, which specifies the bypass tunnelidentifier that was specified by the bypass in use signaling objectbeing acknowledged. In this way, by using the bypass tunnel identifierthat was previously provided by PLR router 16A to MP router 16B in thePath messages before the failure to associate the protected LSPs withbypass tunnel 26, MP router 16B is able to send only a single message toallow PLR router 16A to create backup LSP state for all of the protectedLSPs that routers 16A, 16B have associated with the same bypass tunnelidentifier for bypass tunnel 26. This can reduce the number of messagesthat routers 16 need to send and receive after a failure, and allows forgreater scalability in terms of the number of LSPs that can be used innetwork 14 between PLR router 16A and MP router 16B. PLR router 16Areceives the single Resv message from MP router 16B (130), and inresponse, bypass info module 56 of PLR router 16A creates backup LSPstate 64 for each of the protected LSPs 22 associated with the bypasstunnel identifier (e.g., by referring to bypass tunnel identifiers 58)(132). Bypass info module 56 also includes the previously receivedbackup Resv message-IDs as part of creating the respective backup LSPstate for the protected LSPs being run over bypass tunnel 26.

PLR router 16A subsequently sends summary refresh messages to MP router16B to refresh state for each of LSPs 22 on bypass tunnel 26, where thesummary refresh messages include the backup Path message-IDs that wereincluded in the initial Path messages sent to MP router 16B along withthe bypass tunnel identifier (134). MP router 16B likewise sends summaryrefresh messages to PLR router 16A to refresh state for each of LSPs 22on bypass tunnel 26, where the summary refresh messages include thebackup Resv message-IDs that were included in the initial Resv messagessent to PLR router 16A along with the bypass tunnel identifier (136).PLR router 16A and MP router 16B continue to exchange summary refreshmessages until PLR router 16A determines that the failed resource hasbecome operable (or the primary path between PLR router 16A and MProuter 16B is otherwise back up) (138), at which point PLR router 16Astops sending the summary refresh messages MP router 16B (140). Inresponse to no longer receiving the summary refresh messages from PLRrouter 16A, MP router 16B likewise stops sending summary refreshmessages to PLR router 16A (142).

The techniques described in this disclosure may be implemented, at leastin part, in hardware, software, firmware or any combination thereof. Forexample, various aspects of the described techniques may be implementedwithin one or more processors, including one or more microprocessors,digital signal processors (DSPs), application specific integratedcircuits (ASICs), field programmable gate arrays (FPGAs), or any otherequivalent integrated or discrete logic circuitry, as well as anycombinations of such components. The term “processor” or “processingcircuitry” may generally refer to any of the foregoing logic circuitry,alone or in combination with other logic circuitry, or any otherequivalent circuitry. A control unit comprising hardware may alsoperform one or more of the techniques of this disclosure.

Such hardware, software, and firmware may be implemented within the samedevice or within separate devices to support the various operations andfunctions described in this disclosure. In addition, any of thedescribed units, modules or components may be implemented together orseparately as discrete but interoperable logic devices. Depiction ofdifferent features as modules or units is intended to highlightdifferent functional aspects and does not necessarily imply that suchmodules or units must be realized by separate hardware or softwarecomponents. Rather, functionality associated with one or more modules orunits may be performed by separate hardware or software components, orintegrated within common or separate hardware or software components.

The techniques described in this disclosure may also be embodied orencoded in a computer-readable medium, such as a computer-readablestorage medium, containing instructions. Instructions embedded orencoded in a computer-readable medium may cause a programmableprocessor, or other processor, to perform the method, e.g., when theinstructions are executed. Computer-readable media may includenon-transitory computer-readable storage media and transientcommunication media. Computer readable storage media, which is tangibleand non-transitory, may include random access memory (RAM), read onlymemory (ROM), programmable read only memory (PROM), erasableprogrammable read only memory (EPROM), electronically erasableprogrammable read only memory (EEPROM), flash memory, a hard disk, aCD-ROM, a floppy disk, a cassette, magnetic media, optical media, orother computer-readable storage media. It should be understood that theterm “computer-readable storage media” refers to physical storage media,and not signals, carrier waves, or other transient media.

Various aspects of this disclosure have been described. These and otheraspects are within the scope of the following claims.

The invention claimed is:
 1. A method comprising: receiving, by a mergepoint network device, a plurality of resource reservation requestmessages for establishing a plurality of protected label switched paths(LSPs) that include a protected resource between a common point of localrepair network device and the merge point network device, wherein eachof the resource reservation request messages includes a common bypasstunnel identifier that identifies a common bypass tunnel that extendsbetween the point of local repair network device and the merge pointnetwork device and avoids the protected resource; in response toreceiving the plurality of resource reservation request messages,storing, by the merge point network device, an association between thebypass tunnel identifier and each of the plurality of protected LSPs;receiving, by the merge point network device, a single message over thebypass tunnel to trigger creation of backup LSP state information for aplurality of backup LSPs corresponding to the plurality of protectedLSPs, wherein the single message includes the bypass tunnel identifier;determining, by the merge point network device, that the bypass tunnelidentifier included in the single message is the same as the bypasstunnel identifier of the stored association; and in response to thedetermining, automatically creating, by the merge point network device,backup LSP state information for each of the plurality of backup LSPscorresponding to the plurality of protected LSPs associated with thebypass tunnel identifier according to the stored association.
 2. Themethod of claim 1, further comprising: outputting, by the merge pointnetwork device, a respective resource reservation response message inresponse to each of the plurality of resource reservation requestmessages, wherein each of the resource reservation response messagesincludes the bypass tunnel identifier that identifies the bypass tunnel.3. The method of claim 2, wherein each of the resource reservationresponse messages includes a respective message identifier (ID) to bestored by the point of local repair network device for processingsubsequently received summary refresh messages for backup LSPs for theplurality of protected LSPs.
 4. The method of claim 3, wherein each ofthe plurality of resource reservation request messages includes arespective message identifier (ID) to be stored by the merge pointnetwork device for processing subsequently received summary refreshmessages for the plurality of backup LSPs corresponding to the pluralityof protected LSPs, the method further comprising: sending, by the mergepoint network device, summary refresh messages for each of the pluralityof protected LSPs to the point of local repair network device, whereinthe summary refresh messages include the message IDs indicated by theresource reservation response messages.
 5. The method of claim 4,further comprising: by the merge point network device, in response todetermining that no summary refresh messages have been received from thepoint of local repair network device for one or more of the LSPs withina time period, discontinuing sending the summary refresh messages forthe one or more LSPs.
 6. The method of claim 1, further comprising: inresponse to receiving the single message, and by the merge point networkdevice, sending a single reply message over the bypass tunnel to triggercreation of backup LSP state information at the point of local repairnetwork device for the plurality of backup LSPs corresponding to theplurality of protected LSPs, wherein the single reply message includesthe bypass tunnel identifier that identifies the bypass tunnel.
 7. Themethod of claim 1, wherein receiving the plurality of resourcereservation request messages comprises receiving a plurality of ResourceReservation Protocol with Traffic Engineering extensions (RSVP-TE) Pathmessages, and wherein receiving the single message comprises receiving asingle RSVP-TE Path message for signaling the bypass tunnel.
 8. Themethod of claim 1, further comprising: outputting, by the point of localrepair network device, the plurality of resource reservation requestmessages for establishing the plurality of protected LSPs; by the pointof local repair network device, detecting failure of the protectedresource along the plurality of protected LSPs between the point oflocal repair network device and the merge point network device; and inresponse to detecting the failure, and by the point of local repairnetwork device, outputting the single message over the bypass tunnel tothe merge point network device to trigger creation at the merge pointnetwork device of backup LSP state information for the plurality ofbackup LSPs corresponding to the plurality of protected LSPs, whereinthe single message includes the bypass tunnel identifier.
 9. The methodof claim 1, wherein the single message that includes the bypass tunnelidentifier is encapsulated with a Multi-Protocol Label Switching (MPLS)label associated with the bypass tunnel.
 10. A method comprising:outputting, by a point of local repair network device, a plurality ofresource reservation request messages for establishing a plurality ofprotected label switched paths (LSPs) that include a protected resourcebetween the point of local repair network device and a common mergepoint network device, wherein each of the resource reservation requestmessages includes a common bypass tunnel identifier that identifies acommon bypass tunnel that extends between the point of local repairnetwork device and the merge point network device and avoids theprotected resource; storing, by the point of local repair networkdevice, an association between the bypass tunnel identifier and each ofthe plurality of protected LSPs; by the point of local repair networkdevice, detecting failure of the protected resource along the pluralityof protected LSPs between the point of local repair network device andthe merge point network device; in response to detecting the failure,and by the point of local repair network device, outputting a singlemessage over the bypass tunnel to the merge point network device totrigger creation at the merge point network device of backup LSP stateinformation for a plurality of backup LSPs corresponding to theplurality of protected LSPs, wherein the single message includes thebypass tunnel identifier; receiving, by the point of local repairnetwork device, a single reply message from the merge point networkdevice in response to the single message, wherein the single replymessage includes the bypass tunnel identifier that identifies the bypasstunnel; determining, by the point of local repair network device, thatthe bypass tunnel identifier included in the single message is the sameas the bypass tunnel identifier of the stored association; and inresponse to the determining, automatically creating, by the point oflocal repair network device, backup LSP state information for theplurality of backup LSPs corresponding to the plurality of protectedLSPs.
 11. The method of claim 10, wherein each of the plurality ofresource reservation request messages includes a respective messageidentifier (ID) to be stored by the merge point network device forprocessing subsequently received summary refresh messages for theplurality of backup LSPs corresponding to the plurality of protectedLSPs.
 12. The method of claim 10, wherein outputting the single messagecomprises outputting a single Resource Reservation Protocol with TrafficEngineering extensions (RSVP-TE) Path message to the merge point networkdevice for signaling the bypass tunnel, wherein outputting the pluralityof resource reservation request messages comprises outputting aplurality of Resource Reservation Protocol with Traffic Engineeringextensions (RSVP-TE) Path messages to the merge point network devicealong a path that includes the protected resource, and whereinoutputting a single message comprises outputting a message encapsulatedwith a Multi-Protocol Label Switching (MPLS) label associated with thebypass tunnel.
 13. The method of claim 10, further comprising: aftersending the single message, sending, by the point of local repairnetwork device, summary refresh messages to the merge point networkdevice to refresh state for the plurality of backup LSPs along thebypass tunnel without sending individual trigger resource reservationrequest messages for each of the backup LSPs; and by the point of localrepair network device, in response to determining that the protectedresource has become operable, discontinuing sending the summary refreshmessages for the plurality of backup LSPs.
 14. The method of claim 10,further comprising: receiving, by the point of local repair networkdevice, a plurality of resource reservation reply messages sent by themerge point network device in response to the plurality of resourcereservation request messages, wherein each of the plurality of resourcereservation reply messages includes a bypass information acknowledgementsignaling object that specifies the bypass tunnel identifier; inresponse to receiving the plurality of resource reservation replymessages, storing, by the point of local repair network device,information indicating the protected LSPs for which resource reservationreply messages with the bypass information acknowledgement signalingobject have been received; and for any of the plurality of protectedLSPs that the point of local repair network device has not received aresource reservation reply message with the bypass informationacknowledgement signaling object, sending, in response to detecting thefailure, and by the point of local repair network device, a separatetrigger resource reservation request message, wherein the triggerresource reservation request message does not include a bypassinformation acknowledgment signaling object.
 15. The method of claim 10,further comprising: assigning, by the point of local repair networkdevice, the bypass tunnel identifier that identifies the bypass tunnel.16. The method of claim 10, wherein the merge point network devicecomprises a first merge point network device, wherein the bypass tunnelcomprises a first bypass tunnel, and wherein the bypass tunnelidentifier comprises a first bypass tunnel identifier, the methodfurther comprising: sending, by the point of local repair networkdevice, a resource reservation request message for establishing an LSPhaving a second merge point network device, and that will use a secondbypass tunnel between the point of local repair network device and thesecond merge point network device; and assigning, by the point of localrepair network device, a second bypass tunnel identifier to the secondbypass tunnel.
 17. A merge point network device comprising: one or moreprocessors coupled to a memory; a resource reservation module configuredfor execution by the one or more processors to: receive a plurality ofresource reservation request messages for establishing a plurality ofprotected label switched paths (LSPs) that include a protected resourcebetween a common point of local repair network device and the mergepoint network device, wherein each of the resource reservation requestmessages includes a common bypass tunnel identifier that identifies acommon bypass tunnel that extends between the point of local repairnetwork device and the merge point network device and avoids theprotected resource, store an association between the bypass tunnelidentifier and each of the plurality of protected LSPs in response toreceiving the plurality of resource reservation request messages,receive a single message from the point of local repair network deviceover the bypass tunnel to trigger creation of backup LSP stateinformation for a plurality of backup LSPs corresponding to theplurality of protected LSPs, wherein the single message includes thebypass tunnel identifier, determine that the bypass tunnel identifierincluded in the single message is the same as the bypass tunnelidentifier of the stored association, and in response to thedetermining, create backup LSP state information for each of theplurality of backup LSPs corresponding to the plurality of protectedLSPs associated with the bypass tunnel identifier according to thestored association.
 18. The merge point network device of claim 17,wherein the resource reservation module is configured for execution bythe one or more processors to: in response to receiving the singlemessage, send a single reply message over the bypass tunnel to triggercreation of backup LSP state information at the point of local repairnetwork device for a plurality of backup LSPs corresponding to theplurality of protected LSPs, wherein the single reply message includesthe bypass tunnel identifier that identifies the bypass tunnel.
 19. Themerge point network device of claim 17, wherein the plurality ofresource reservation request messages comprises a plurality of ResourceReservation Protocol with Traffic Engineering extensions (RSVP-TE) Pathmessages, and wherein the single message comprises a single RSVP-TE Pathmessage.
 20. The merge point network device of claim 17, wherein thesingle message is encapsulated with a Multi-Protocol Label Switching(MPLS) label associated with the bypass tunnel.